A typical multiple-zone heat pump refrigerant system includes a single outdoor heat pump unit connected to multiple indoor units. The indoor units are often individually-controlled split-type heating/cooling units.
In many implementations, the outdoor heat pump unit may be limited to a single mode of operation. In other words, such an outdoor heat pump unit must be in either a heating mode or a cooling mode at any given time, but cannot be in both. The multiple indoor units can each have a different operational mode (i.e., heating or cooling), but need not all be in the same operational mode at the same time.
This means that in some situations, a subset of the connected indoor units may be in a heating mode, while a different subset of the indoor units may be in a cooling mode, with each indoor unit being only in a single mode (i.e., heating or cooling). In such a situation, the indoor units in the heating mode are requesting heating from the outdoor heat pump unit, while the indoor units in the cooling mode are requesting cooling from the outdoor heat pump unit. However, the typical multi-zone outdoor unit can only accommodate one set of requests. This is particularly common for multiple-zone systems during the shoulder seasons of spring and autumn.
The current state-of-the-art involves keeping the entire system, including the outdoor heat pump unit, in the current mode (heating or cooling) until all of the indoor units exit that particular mode. Only when all of the indoor units change mode will the outdoor heat pump unit change its mode of operation. In other words, if the outdoor heat pump unit is in a heating mode, it will not change to a cooling mode until all of the indoor units change to a cooling mode (i.e., until all of the indoor units request cooling from the outdoor heat pump unit).
This can cause a problem for homeowners in that an individual zone can force the entire system to remain in a particular operational mode (heating or cooling) even when all of the other zones in the house require the other mode. For example, if the outdoor heat pump unit is in a cooling mode, every indoor unit but one is in a heating mode (requesting heating from the outdoor heat pump unit) and a single indoor unit is in a cooling mode (requesting cooling from the outdoor heat pump unit) the outdoor heat pump unit will remain in a cooling mode for as long as that last indoor unit is in the cooling mode.
It would therefore be desirable to provide a way to improve the decision-making process to allow for an air conditioning system to switch between heating and cooling modes for an outdoor heat pump unit in a way that more closely matches the desires of a homeowner or building manager.